# Case Report: CD19 CAR-T therapy induces dual remission in AML-M2b patient with CNS-PTLD and relapse

## TL;DR

CD19 CAR-T therapy successfully treated a rare case of AML relapse and CNS-PTLD in a patient after stem cell transplant.

## Contribution

Demonstrates CD19 CAR-T therapy's efficacy in treating both AML-M2b relapse and CNS-PTLD via shared antigen targeting.

## Key findings

- CD19 CAR-T therapy achieved complete remission in a patient with AML-M2b and CNS-PTLD.
- Treatment resulted in disappearance of fusion gene and extramedullary lesions with manageable side effects.
- Shared CD19 expression enabled a single CAR-T product to target multiple malignancies.

## Abstract

Acute myeloid leukemia (AML)-M2b with t(8;21)(q22;q22)/RUNX1::RUNX1T1 (AML1-ETO) is associated with a high risk of relapse after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Post-transplant lymphoproliferative disorder (PTLD), particularly involving the central nervous system (CNS), confers a poor prognosis. Although CD19 chimeric antigen receptor T-cell (CAR-T) therapy is established in B-cell malignancies, its application in acute myeloid leukemia (AML) or CNS-PTLD has rarely been reported.

A 24-year-old male with AML-M2b showed persistent RUNX1::RUNX1T1 (AML1-ETO) positivity after allo-HSCT. He developed an extramedullary relapse (presacral mass) at 7 months, followed by CNS-PTLD with limb palsy at 9 months post-HSCT. The disease subsequently progressed to bone marrow relapse (RUNX1::RUNX1T1 94.42%, MRD >5%).

Given the co-expression of CD19 on both the AML and PTLD cells, the patient was treated with donor-derived CD19 CAR-T cells. He experienced manageable grade 1 cytokine release syndrome (CRS) and grade 3 Immune Effector Cell-Associated Neurotoxicity Syndrome (ICANS).

The patient achieved a complete response (CR) with negative MRD, disappearance of the fusion gene, reduction of PTLD and extramedullary lesions, and recovery of limb strength.

This case demonstrates the efficacy and feasibility of CD19 CAR-T therapy for concomitant post-transplant AML-M2b relapse and CNS-PTLD, leveraging their shared CD19 expression. It provides clinical evidence that targeting a shared antigen with a single CAR-T product can effectively treat heterogeneous malignancies, offering a promising new strategy for such complex cases.